FEATURES
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LTC3417
Dual Synchronous
1.4A/800mA 4MHz
Step-Down DC/DC Regulator
DESCRIPTION
The LTC
®
3417 is a dual constant frequency, synchronous
step-down DC/DC converter. Intended for medium power
applications, it operates from a 2.25V to 5.5V input volt-
age range and has a constant programmable switching
frequency, allowing the use of tiny, low cost capacitors
and inductors 2mm or less in height. Each output voltage
is adjustable from 0.8V to 5V. Internal synchronous low
R
DS(ON)
power switches provide high efficiency without
the need for external Schottky diodes.
A user selectable mode input allows the user to trade
off ripple voltage for light load efficiency. Burst Mode
®
operation provides high efficiency at light loads, while
Pulse Skip mode provides low ripple noise at light loads.
A phase mode pin allows the second channel to operate
in-phase or 180° out-of-phase with respect to channel 1.
Out-of-phase operation produces lower RMS current on
V
IN
and thus lower RMS derating on the input capacitor.
To further maximize battery life, the P-channel MOSFETs
are turned on continuously in dropout (100% duty cycle)
and both channels draw a total quiescent current of only
125μA. In shutdown, the device draws <1μA.
L,
LT, LTC, LTM and Burst Mode are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners. Protected by U.S. Patents
including 5481178, 6580258, 6304066, 6127815, 6498466, 6611131, 6144194.
High Efficiency: Up to 95%
1.4A/800mA Guaranteed Minimum Output Current
No Schottky Diodes Required
Programmable Frequency Operation: 1.5MHz or
Adjustable From 0.6MHz to 4MHz
Low R
DS(ON)
Internal Switches
Short-Circuit Protected
V
IN
: 2.25V to 5.5V
Current Mode Operation for Excellent Line and
Load Transient Response
125μA Quiescent Current in Sleep Mode
Ultralow Shutdown Current: I
Q
< 1μA
Low Dropout Operation: 100% Duty Cycle
Power Good Output
Phase Pin Selects 2nd Channel Phase Relationship
with Respect to 1st Channel
Internal Soft-Start with Individual Run Pin Control
Available in Small Thermally Enhanced
(5mm
×
3mm) DFN and 20-Lead TSSOP Packages
APPLICATIONS
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PDAs/Palmtop PCs
Digital Cameras
Cellular Phones
PC Cards
Wireless and DSL Modems
TYPICAL APPLICATION
V
IN
2.5V TO 5.5V
10μF
V
OUT1
1.8V
1.4A
1.5μH
22pF
V
IN
511k
V
FB1
22μF
412k
I
TH1
5.9k
2200pF
GND
I
TH2
2.87k
6800pF
3417 TA01
OUT2 Efficiency
(Burst Mode Operation)
100
REFER TO FIGURE 4
10
95
2.2μH
EFFICIENCY (%)
V
IN
FREQ
SW1
RUN1
LTC3417
V
FB2
SW2
RUN2
V
IN
866k
412k
10μF
V
OUT2
2.5V
800mA
1
EFFICIENCY
POWER LOSS (W)
90
0.1
85
0.01
80
75
70
0.001
POWER LOSS
V
IN
= 3.6V
V
OUT
= 2.5V
FREQ = 1MHz
0.01
0.1
LOAD CURRENT (A)
1
3417 TA01a
22pF
0.001
0.0001
3417fd
1
LTC3417
ABSOLUTE MAXIMUM RATINGS
(Note 1)
V
IN1
, V
IN2
Voltages ...................................... – 0.3V to 6V
MODE, SW1, SW2, RUN1,
RUN2, V
FB1
, V
FB2
, PHASE, FREQ,
I
TH1
, I
TH2
Voltages............... –0.3V to (V
IN1
/V
IN2
+ 0.3V)
V
IN1
– V
IN2
, V
IN2
– V
IN1
.......................................... 0.3V
PGOOD Voltage ........................................... –0.3V to 6V
Operating Ambient Temperature Range
(Note 2) .................................................. –40°C to 85°C
Junction Temperature (Notes 7, 8) ...................... 125°C
Storage Temperature Range
DFN Package..................................... –65°C to 125°C
TSSOP Package ................................ –65°C to 150°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
RUN1
V
IN1
ITH1
V
FB1
V
FB2
I
TH2
RUN2
V
IN2
1
2
3
4
5
6
7
8
17
16 PGND1
15 SW1
14 PHASE
13 GNDA
12 FREQ
11 PGOOD
10 SW2
9
MODE
GNDD
RUN1
V
IN1
I
TH1
V
FB1
V
FB2
I
TH2
RUN2
V
IN2
1
2
3
4
5
6
7
8
9
21
20 GNDD
19 PGND1
18 SW1
17 PHASE
16 GNDA
15 FREQ
14 PGOOD
13 SW2
12 MODE
11 PGND2
PGND2 10
DHC PACKAGE
16-LEAD (3mm
×
5mm) PLASTIC DFN
T
JMAX
= 125°C,
θ
JA
= 43°C/W
EXPOSED PAD (PIN 17) IS PGND2/GNDD, MUST BE SOLDERED TO PCB
FE PACKAGE
20-LEAD PLASTIC TSSOP
T
JMAX
= 150°C,
θ
JA
= 38°C/W
EXPOSED PAD (PIN 21) IS PGND2/GNDD, MUST BE SOLDERED TO PCB
ORDER INFORMATION
LEAD FREE FINISH
LTC3417EDHC#PBF
LTC3417EFE#PBF
LEAD BASED FINISH
LTC3417EDHC
LTC3417EFE
TAPE AND REEL
LTC3417EDHC#TRPBF
LTC3417EFE#TRPBF
TAPE AND REEL
LTC3417EDHC#TR
LTC3417EFE#TR
PART MARKING
3417
LTC3417EFE
PART MARKING
3417
LTC3417EFE
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic DFN
20-Lead Plastic TSSOP
PACKAGE DESCRIPTION
16-Lead (3mm
×
3mm) Plastic DFN
20-Lead Plastic TSSOP
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
TEMPERATURE RANGE
–40°C to 85°C
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
For more information on lead free part marking, go to:
http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to:
http://www.linear.com/tapeandreel/
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V unless otherwise specified. (Note 2)
SYMBOL
V
IN1
, V
IN2
I
FB1
, I
FB2
V
FB1
, V
FB2
ΔV
LINEREG
V
LOADREG
PARAMETER
Operating Voltage Range
Feedback Pin Input Current
Feedback Voltage
Reference Voltage Line Regulation. %/V is the
Percentage Change in V
OUT
with a Change in V
IN
Output Voltage Load Regulation
CONDITIONS
V
IN1
= V
IN2
(Note 3)
(Note 3)
V
IN
= 2.25V to 5V (Note 3)
I
TH1
, I
TH2
= 0.36V (Note 3)
I
TH1
, I
TH2
= 0.84V (Note 3)
●
●
ELECTRICAL CHARACTERISTICS
MIN
2.25
0.784
TYP
MAX
5.5
± 0.1
UNITS
V
μA
V
%/V
%
%
3417fd
0.8
0.04
0.02
–0.02
0.816
0.2
0.2
–0.2
2
LTC3417
ELECTRICAL CHARACTERISTICS
SYMBOL
g
m(EA)
I
S
PARAMETER
Error Amplifier Transconductance
Input DC Supply Current (Note 4)
Active Mode
Half Active Mode (V
RUN2
= 0V, 1.4A Only)
Half Active Mode (V
RUN1
= 0V, 800mA Only)
Both Channels in Sleep Mode
Shutdown
f
OSC
Oscillator Frequency
The
l
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
IN
= 3.6V unless otherwise specified. (Note 2)
CONDITIONS
I
TH1
, I
TH2(PINLOAD)
= ±5μA (Note 3)
V
FB1
= V
FB2
= 0.75V, V
MODE
= V
IN
,
V
RUN1
= V
RUN2
= V
IN
V
FB1
= 0.75V, V
MODE
= V
IN
, V
RUN1
= V
IN
V
FB2
= 0.75V, V
MODE
= V
IN
, V
RUN2
= V
IN
V
FB1
= V
FB2
= 1V, V
MODE
= V
IN
,
V
RUN1
= V
RUN2
= V
IN
V
RUN1
= V
RUN2
= 0V
V
FREQ
= V
IN
V
FREQ
: R
T
= 143k
V
FREQ
: Resistor (Note 6)
1.2
0.85
1.8
1
V
IN1
= 3.6V (Note 5)
V
IN1
= 3.6V (Note 5)
V
IN2
= 3.6V (Note 5)
V
IN2
= 3.6V (Note 5)
V
IN1
= 6V, V
ITH1
= 0V, V
RUN1
= 0V
V
IN2
= 6V, V
ITH2
= 0V, V
RUN2
= 0V
V
IN1
, V
IN2
Ramping Down
V
IN1
, V
IN2
Ramping Up
V
FB1
or V
FB2
Ramping Up
V
FB1
or V
FB2
Ramping Down
1.9
1.95
MIN
TYP
1400
400
260
260
125
0.1
1.5
1
2.25
1.2
0.088
0.084
0.16
0.15
0.01
0.01
2.07
2.12
–6
–6
160
0.3
V
IN
–0.5
0.5
V
IN
= 6V, V
PIN
= 3V
0.01
1
0.5
V
IN
–0.5
V
IN
–0.5
0.85
300
1.5
1
1
2.2
2.25
600
400
400
250
1
1.8
1.25
4
MAX
UNITS
μS
μA
μA
μA
μA
μA
MHz
MHz
MHz
A
A
Ω
Ω
Ω
Ω
μA
μA
V
V
%
%
Ω
V
V
V
μA
V
V
V
I
LIM1
I
LIM2
R
DS(ON)1
R
DS(ON)2
I
SW1(LKG)
I
SW2(LKG)
V
UVLO
T
PGOOD
Peak Switch Current Limit on SW1 (1.4A)
Peak Switch Current Limit on SW2 (800mA)
SW1 Top Switch On-Resistance (1.4A)
SW1 Bottom Switch On-Resistance
SW2 Top Switch On-Resistance (800mA)
SW2 Bottom Switch On-Resistance
Switch Leakage Current SW1 (1.4A)
Switch Leakage Current SW2 (800mA)
Undervoltage Lockout Threshold
Threshold for Power Good. Percentage
Deviation from V
FB
Steady State
(Typically 0.8V)
Power Good Pull-Down On-Resistance
RUN1, RUN2 Threshold
PHASE Threshold High-CMOS Levels
PHASE Threshold Low-CMOS Levels
R
PGOOD
V
RUN1
,
V
RUN2
V
PHASE
I
RUN1
, I
RUN2
, RUN1, RUN2, PHASE and MODE
I
PHASE
, I
MODE
Leakage Current
VTL
MODE
VTH
MODE
VTH
FREQ
MODE Threshold Voltage Low
MODE Threshold Voltage High
FREQ Threshold Voltage High
Note 1:
Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2:
The LTC3417 is guaranteed to meet specified performance from
0°C to 85°C. Specifications over the –40°C to 85°C operating ambient
temperature range are assured by design, characterization and correlation
with statistical process controls.
Note 3:
The LTC3417 is tested in feedback loop which servos V
FB1
to the
midpoint for the error amplifier (V
ITH1
= 0.6V) and V
FB2
to the midpoint for
the error amplifier (V
ITH2
= 0.6V).
Note 4:
Total supply current is higher due to the internal gate charge being
delivered at the switching frequency.
Note 5:
Switch on-resistance is guaranteed by design and test correlation
on the DHC package and by final test correlation on the FE package.
Note 6:
Variable frequency operation with resistor is guaranteed by design
but not production tested and is subject to duty cycle limitations.
Note 7:
This IC includes overtemperature protection that is intended
to protect the device during momentary overload conditions. Junction
temperature will exceed 125°C when overtemperature protection is active.
Continuous operation above the specified maximum operating junction
temperature may impair device reliability.
Note 8:
T
J
is calculated from the ambient temperature, T
A
, and power dis-
sipation, P
D
, according to the following formula:
LTC3417EDHC: T
J
= T
A
+ (P
D
• 43°C/W)
LTC3417EFE: T
J
= T
A
+ (P
D
• 38°C/W)
3417fd
3
LTC3417
TYPICAL PERFORMANCE CHARACTERISTICS
OUT1 Burst Mode Operation
OUT1 Pulse Skipping
Mode Operation
OUT1 Forced Continuous
Mode Operation
V
OUT
20mV/DIV
V
OUT
20mV/DIV
V
OUT
20mV/DIV
I
L
250mA/DIV
I
L
250mA/DIV
I
L
250mA/DIV
V
IN
= 3.6V
2μs/DIV
V
OUT
= 1.8V
I
LOAD
= 100mA
REFER TO FIGURE 4
3417 G01
2μs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 100mA
REFER TO FIGURE 4
3417 G02
2μs/DIV
V
IN
= 3.6V
V
OUT
= 1.8V
I
LOAD
= 100mA
REFER TO FIGURE 4
3417 G03
OUT2 Burst Mode Operation
OUT2 Pulse Skipping
Mode Operation
OUT2 Forced Continuous
Mode Operation
V
OUT
20mV/DIV
V
OUT
20mV/DIV
V
OUT
20mV/DIV
I
L
250mA/DIV
I
L
250mA/DIV
I
L
250mA/DIV
2μs/DIV
V
IN
= 3.6V
V
OUT
= 2.5V
I
LOAD
= 60mA
REFER TO FIGURE 4
3417 G04
2μs/DIV
V
IN
= 3.6V
V
OUT
= 2.5V
I
LOAD
= 60mA
REFER TO FIGURE 4
3417 G05
2μs/DIV
V
IN
= 3.6V
V
OUT
= 2.5V
I
LOAD
= 60mA
REFER TO FIGURE 4
3417 G06
OUT1 Efficiency vs Load Current
100
V
IN
= 2.5V
95 V
OUT
= 1.8V
90
EFFICIENCY (%)
EFFICIENCY (%)
85
80
75
70
65
60
0.001
0.01
0.1
Burst Mode
OPERATION
PULSE SKIP
FORCED
CONTINUOUS
REFER TO FIGURE 4
1
10
3417 G07
OUT2 Efficiency vs Load Current
100
V
IN
= 3.6V
V
OUT
= 2.5V
95
90
85
80
75
70
65
60
0.001
0.01
Burst Mode
OPERATION
PULSE SKIP
FORCED
CONTINUOUS
REFER TO FIGURE 4
0.1
1
LOAD CURRENT (A)
3417 G08
OUT1 Efficiency vs V
IN
(Burst Mode Operation)
100
95
EFFICIENCY (%)
90
I
LOAD
= 1.4A
85
80
75
70
2
2.5
3
3.5
REFER TO FIGURE 4
4
4.5
5
5.5
3417 G09
V
OUT
= 1.8V
I
LOAD
= 460mA
LOAD CURRENT (A)
V
IN
(V)
3417fd
4
LTC3417
TYPICAL PERFORMANCE CHARACTERISTICS
OUT2 Efficiency vs V
IN
(Pulse Skipping Mode)
100
I
LOAD
= 250mA
95
EFFICIENCY (%)
90
85
80
75
70
2
2.5
3
3.5
V
OUT
= 2.5V
REFER TO FIGURE 4
4
4.5
5
5.5
I
LOAD
= 800mA
V
OUT1
100mV/DIV
V
OUT2
100mV/DIV
Load Step OUT1
Load Step OUT2
I
OUT1
500mA/DIV
I
OUT2
500mA/DIV
V
IN
= 3.6V
100μs/DIV
V
OUT
= 1.8V
I
LOAD
= 0.25A to 1.4A
REFER TO FIGURE 4
3417 G11
V
IN
= 3.6V
100μs/DIV
V
OUT
= 2.5V
I
LOAD
= 0.25A to 0.8A
REFER TO FIGURE 4
3417 G12
V
IN
(V)
3417 G10
Efficiency vs Frequency OUT1
94
92
EFFICIENCY (%)
90
88
86
84
82
0
1
2
3
4
5
FREQUENCY (MHz)
3417 G13
Efficiency vs Frequency OUT2
90
85
EFFICIENCY (%)
80
75
70
65
60
0
1
2
FREQUENCY (MHz)
3417 G14
R
DS(ON)
vs V
IN
OUT1
0.105
T
A =
27°C
T
A
= 27°C
V
IN
= 3.6V
V
OUT
= 1.8V
I
OUT
= 300mA
0.100
P-CHANNEL SWITCH
R
DS(ON)
(Ω)
T
A
= 27°C
V
IN
= 3.6V
V
OUT
= 2.5V
I
OUT
= 100mA
3
4
0.095
0.090
0.085
N-CHANNEL SWITCH
0.080
2
2.5
3
3.5
4
4.5
5
5.5
V
IN
(V)
3417 G15
R
DS(ON)
vs V
IN
OUT2
0.20
0.19
0.18
R
DS(ON)
(Ω)
0.17
0.16
0.15
N-CHANNEL SWITCH
0.14
2
2.5
3
3.5
4
4.5
5
5.5
V
IN
(V)
3417 G16
Frequency vs V
IN
T
A
= 27°C
FREQUENCY VARIATION (%)
6
4
15
10
5
0
Frequency vs Temperature
P-CHANNEL SWITCH
2
0
–2
–4
FREQ = 143k TO GROUND
FREQUENCY VARIATION (%)
FREQ = V
IN
FREQ = 143k TO GROUND
–5
–10
FREQ = V
IN
–6
–8
–10
2
2.5
3
3.5
4
4.5
5
5.5
–15
–50 –25
0
25
50
75
100
125
V
IN
(V)
3417 G17
TEMPERATURE (°C)
3417 G18
3417fd
5
嵌入式系统
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